/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.engine.flush;

import org.apache.iotdb.commons.concurrent.WrappedRunnable;
import org.apache.iotdb.commons.exception.StartupException;
import org.apache.iotdb.commons.service.IService;
import org.apache.iotdb.commons.service.JMXService;
import org.apache.iotdb.commons.service.ServiceType;
import org.apache.iotdb.commons.service.metric.MetricService;
import org.apache.iotdb.db.conf.IoTDBConfig;
import org.apache.iotdb.db.conf.IoTDBDescriptor;
import org.apache.iotdb.db.engine.flush.pool.FlushSubTaskPoolManager;
import org.apache.iotdb.db.engine.flush.pool.FlushTaskPoolManager;
import org.apache.iotdb.db.engine.storagegroup.TsFileProcessor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.concurrent.ConcurrentLinkedDeque;

public class FlushManager implements FlushManagerMBean, IService {

    private static final Logger LOGGER = LoggerFactory.getLogger(FlushManager.class);
    private final IoTDBConfig config = IoTDBDescriptor.getInstance().getConfig();

    private ConcurrentLinkedDeque<TsFileProcessor> tsFileProcessorQueue =
            new ConcurrentLinkedDeque<>();

    private FlushTaskPoolManager flushPool = FlushTaskPoolManager.getInstance();

    @Override
    public void start() throws StartupException {
        FlushSubTaskPoolManager.getInstance().start();
        flushPool.start();
        try {
            JMXService.registerMBean(this, ServiceType.FLUSH_SERVICE.getJmxName());
            MetricService.getInstance().addMetricSet(new FlushManagerMetrics(this));
        } catch (Exception e) {
            throw new StartupException(this.getID().getName(), e.getMessage());
        }
    }

    @Override
    public void stop() {
        FlushSubTaskPoolManager.getInstance().stop();
        FlushTaskPoolManager.getInstance().stop();
        JMXService.deregisterMBean(ServiceType.FLUSH_SERVICE.getJmxName());
    }

    @Override
    public ServiceType getID() {
        return ServiceType.FLUSH_SERVICE;
    }

    @Override
    public int getNumberOfWaitingTasks() {
        return flushPool.getWaitingTasksNumber();
    }

    @Override
    public int getNumberOfWorkingTasks() {
        return flushPool.getWorkingTasksNumber();
    }

    @Override
    public int getNumberOfPendingTasks() {
        return flushPool.getWaitingTasksNumber();
    }

    @Override
    public int getNumberOfWorkingSubTasks() {
        return FlushSubTaskPoolManager.getInstance().getWorkingTasksNumber();
    }

    @Override
    public int getNumberOfPendingSubTasks() {
        return FlushSubTaskPoolManager.getInstance().getWaitingTasksNumber();
    }

    /**
     * a flush thread handles flush task
     */
    class FlushThread extends WrappedRunnable {

        @Override
        public void runMayThrow() {
            TsFileProcessor tsFileProcessor = tsFileProcessorQueue.poll();
            if (null == tsFileProcessor) {
                return;
            }

            tsFileProcessor.flushOneMemTable();
            tsFileProcessor.setManagedByFlushManager(false);
            if (LOGGER.isDebugEnabled()) {
                LOGGER.debug(
                        "Flush Thread re-register TSProcessor {} to the queue.",
                        tsFileProcessor.getTsFileResource().getTsFile().getAbsolutePath());
            }
            registerTsFileProcessor(tsFileProcessor);
        }
    }

    /**
     * Add tsFileProcessor to asyncTryToFlush manager
     *
     * @param tsFileProcessor tsFileProcessor to be flushed
     */
    @SuppressWarnings("squid:S2445")
    public void registerTsFileProcessor(TsFileProcessor tsFileProcessor) {
        synchronized (tsFileProcessor) {
            if (tsFileProcessor.isManagedByFlushManager()) {
                LOGGER.debug(
                        "{} is already in the flushPool, the given processor flushMemtable number = {}",
                        tsFileProcessor.getTsFileResource().getTsFile().getAbsolutePath(),
                        tsFileProcessor.getFlushingMemTableSize());
            } else {
                if (tsFileProcessor.getFlushingMemTableSize() > 0) {
                    tsFileProcessorQueue.add(tsFileProcessor);
                    if (LOGGER.isDebugEnabled()) {
                        LOGGER.debug(
                                "{} begin to submit a flush thread, flushing memtable size: {}, queue size: {}",
                                tsFileProcessor.getTsFileResource().getTsFile().getAbsolutePath(),
                                tsFileProcessor.getFlushingMemTableSize(),
                                tsFileProcessorQueue.size());
                    }
                    tsFileProcessor.setManagedByFlushManager(true);
                    flushPool.submit(new FlushThread());
                } else {
                    if (LOGGER.isDebugEnabled()) {
                        LOGGER.debug(
                                "No flushing memetable to do, register TsProcessor {} failed.",
                                tsFileProcessor.getTsFileResource().getTsFile().getAbsolutePath());
                    }
                }
            }
        }
    }

    private FlushManager() {
    }

    public static FlushManager getInstance() {
        return InstanceHolder.instance;
    }

    private static class InstanceHolder {

        private InstanceHolder() {
        }

        private static FlushManager instance = new FlushManager();
    }

    @Override
    public String toString() {
        return String.format(
                "TSProcessors in the queue: %d, TaskPool size %d + %d,",
                tsFileProcessorQueue.size(),
                flushPool.getWorkingTasksNumber(),
                flushPool.getWaitingTasksNumber());
    }
}
